Validate character count

Check weighted character count per platform and whether the text is within each platform's limit.

Twitter/X uses weighted counting (URLs = 23 chars via t.co, emojis = 2 chars). All other platforms use plain character length.

Returns counts and limits for all 15 supported platform variants.

X (Twitter) returns two rows and this endpoint cannot tell you which one applies to you: it takes only text, so it never resolves an account. twitter (280) is the free tier limit. twitterPremium (25000) applies only when the target X account has a paid X subscription, and publishing enforces 280 instead for any post carrying a poll (this endpoint has no poll input, so the twitterPremium row always shows 25000). A free account trusting the twitterPremium row can pass validation here and still fail at publish time, where the account's real limit is enforced.

To validate against the per-account limit, use POST /v1/tools/validate/post instead: it accepts an accountId per platform entry, resolves X Premium status, and checks the text against the limit publishing enforces, including the poll cap. A missing, foreign, or invalid accountId falls back to the conservative 280.